proliferating their products. It is shown that a selective pruning within the cartel always occurs. Moreover, by associating a … cooperative (or coalitional) stability of the whole industry cartel is the equidistance of firms' products along the quality …

. Within this setting, we study four types of price- xing agreement: (i) a segment-wide cartel in the premium submarket only …, (ii) a segment-wide cartel in the standard submarket only, (iii) two segment-wide cartels, and (iv) an industry …-wide cartel. We present a complete characterization of the collusive pricing equilibrium and examine the corresponding effect on …

complementarities. We apply this result to cartel formation in Bertrand oligopoly and in Shapley-Shubik (1977) strategic market games …